GetChannel.java

package org.javacore.nio;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/*
 * Copyright [2015] [Jeff Lee]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @author Jeff Lee
 * @since 2015-10-8 17:33:19
 * 从流中获取FileChannel的案例
 */
public class GetChannel {
	private static final int BSIZE = 1024; // 1K字节
	
	@SuppressWarnings("resource")
	public static void main(String[] args) throws IOException {
		//////
		// 写入文件
		//////
		// 从文件输出流获取FileChannel
		FileChannel fc = new FileOutputStream("data.txt").getChannel();
		// 将含有字节序列的缓冲区写入文件通道
		fc.write(ByteBuffer.wrap("Some Text".getBytes()));// 将已存在的字节数组包装到ByteBuffer
		// 关闭通道
		fc.close();
		
		//////
		// 从文件尾部写入
		//////
		// 从RandomAccessFile获取FileChannel文件
		fc = new RandomAccessFile("data.txt", "rw").getChannel();
		// 文件指针指向文件尾部
		fc.position(fc.size());
		// 将含有字节序列的缓冲区写入文件通道
		fc.write(ByteBuffer.wrap(" Some more".getBytes()));
		// 关闭通道
		fc.close();
		
		//////
		// 读取文件
		//////
		// 从文件输出流获取FileChannel文件
		fc = new FileInputStream("data.txt").getChannel();
		// 分配ByteBuffer的大小 1K
		ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
		// 将字节序列从此通道读入给定的缓冲区。
		fc.read(buffer);
		// 反转缓冲区，为写入或读取做好准备
		buffer.flip();
		// 打印
		while (buffer.hasRemaining()) {
			System.out.print((char)buffer.get());
		}
	}
	
}